This invention relates to conveyorized cooking apparatus and particularly to such apparatus useful in a commercial environment such as a fast service restaurant in which rapidly changing variable loads must be accommodated.
Cooking apparatus have been proposed heretofore in which a serving of foodstuff to be cooked is moved through a cooking zone by a driven conveyor. One example is to be found in prior U.S. Pat. No. 4,176,589, to which the interested reader is referred. To any extent necessary or appropriate to an understanding of this invention, the disclosure of that prior patent is hereby incorporated by reference into the present description.
In such prior apparatus as have come into use, the source of heat often is either a fluid fueled burner or an electrical resistance element. The most commonly used electrical resistance element has been a metal or quartz sheathed tubular or rod-like heating element similar to those indicated at 45 and 46 in the drawings of the aforementioned prior patent. While such cooking apparatus have achieved some success, particularly with beef and meat pattie products such as hamburgers, difficulties have appeared as attempts have been made to apply the technology to other applications.
More particularly, such tubular elements, when used at higher watt densities, produce intense strands or ribbons of heat, and emit heat or thermal energy from all surfaces of the tube. Attempts to cook more quickly cooked foodstuffs such as fish or foodstuffs having combustibles such as butter sauces or bread crumbs using cooking apparatus in accordance with the prior art has resulted in an awareness that the initial development of such apparatus for beef and the like was fortuitous in that such foodstuffs are apparently less sensitive to overcooking and flaming which has been found to easily occur due to the response of the heating elements to thermal load imposed by foodstuff to be cooked. As will be understood by persons of skill in the applicable arts, foodstuff introduced into a cooking zone by a conveyor represents a thermal load on the heating elements, in that the elements must supply the thermal energy necessary to accomplish cooking.
All cooking involves temperature regulation. As such, prior conveyorized cooking apparatus of the types with which this invention is concerned have provided for regulation of the temperatures in the cooking zone through which foodstuff is conveyed, typically by controlling fuel flow or electrical energization. Known controls such as thermostats are used for this purpose. The thermal load imposed by foodstuffs to be cooked results in control being exercised to increase the temperature in the cooking zone.
In environments of use, and particularly in fast service restaurants, such thermal load varies over time. At a busy time, the thermal load of foodstuff may be nearly constant and easily handled by conventional controls. At less busy times, the thermal load varies on a continuum between essentially no-load when no foodstuff is passing through the cooking zone and full load when the cooking zone is filled with foodstuff.
The specific problem addressed by this invention arises when thermal loads are less than full, and most particularly when such loads are relatively light. The problem is compounded where the foodstuff being prepared is more temperature sensitive and quick cooking, such as fish. In such circumstances, servings which are introduced into the cooking zone impose a thermal load and the conventional controls and heaters respond by increasing thermal output. Because of the relatively quick rise time required or desired in order to achieve cooking of the foodstuff, the thermal energy released is relatively great, and (in conventional heaters as used prior to this invention) the thermal mass of the heater receives such portion of the energy as is not applied to cooking the serving of foodstuff. For the usual apparatus operating under light load conditions, an electrical resistance heater is repeatedly and relatively rapidly cycled between low energy and high energy states. The thermal mass of the heater is not capable of accomodating such rapid change and, as a consequence, the thermal mass of the heater is raised to an elevated temperature. This elevated temperature, when encountered by the next following serving of foodstuff, is sufficient to cause cooking at an improper rate (typically too quickly due to excessive temperatures gradually built up over a sequence of cycles such as those described). Thus the foodstuffs prepared during light load conditions are of unsatisfactory quality.
The relative concentration of heat in the ribbons or strands mentioned above contributes to the problem stated above, and also creates still other problems. More particularly, a tubular element emits energy in all directions around the element, thus requiring some form of reflector or the like to direct energy from the "back side" of the element toward the foodstuff being cooked. Such reflectors are thermally inefficient and pose difficulty in accurately determining the cooking temperatures within a cooking zone. The "hot ribbon" effect also increases the tendency of foodstuffs toward flaming.